losing fields during validation - nested serializer create()

[Andrew Olson]

hi everyone,

I don't understand why specific fields are being dropped within validated_data.

I've also posted this question on SO here.

When POSTing input to create() a new instance, the following line:

thisLabel = ClassificationLabel.objects.get(identifier=label.identifier)

the following error is thrown because the identifier attribute is not present:

AttributeError at /api/v1/policies/ 'collections.OrderedDict' object has no attribute 'identifier

I have the following serializers within Django REST framework:

class ClassificationLabelDetailSerializer(serializers.ModelSerializer):
class Meta:
    model = ClassificationLabel
    fields = ('displayName', 'helpText', 'identifier', 'backgroundColour', 'foregroundColour', 'comment', 'description', 'lastChanged', 'revision')
    read_only_fields = ('identifier', 'lastChanged', 'revision',)

class PolicySerializer(serializers.ModelSerializer):
labels = ClassificationLabelDetailSerializer(many=True)
class Meta:
    model = Policy
    fields = ('displayName', 'identifier', 'labels', 'lastChanged', 'description', 'comment')
    read_only_fields = ('identifier', 'lastChanged',)


def create(self,validated_data):
    labelData = validated_data.pop('labels')
    thisPolicy = Policy.objects.create(**validated_data)
    for label in labelData:
        for k, v in label.items():
            print(k, v) #<=this is what I'm using to see what object attributes are available
        thisLabel = ClassificationLabel.objects.get(identifier=label.identifier)#insert organisational filter here
        PolicyMemberClassificationLabel.objects.create(policy=thisPolicy, label=thisLabel, order=index)
    return thisPolicy

when sending the following via POST it's dropping the identifier, lastChanged and revision fields from the nested representation within validated_data. Here's the contents of the POST:

{
  "labels": [
    {
      "displayName": "Test name",
      "helpText": "Wayfarers sartorial authentic, small batch readymade disrupt coloring book. Wayfarers sartorial authentic, small batch readymade disrupt col",
      "identifier": "fa27e9bd-5007-4874-b10c-46b63c7c8a86",
      "backgroundColour": "#808900",
      "foregroundColour": "#000000",
      "comment": "Wayfarers sartorial authentic, small batch readymade disrupt coloring book.",
      "description": "Wayfarers sartorial authentic, small batch readymade disrupt coloring book.",
      "lastChanged": "2017-07-03T09:26:20.450681Z",
      "revision": 2
    },
    {
      "displayName": "Test name 1",
      "helpText": "Wayfarers sartorial authentic, small batch readymade disrupt coloring book.",
      "identifier": "29c968dd-8b83-4374-962d-32b9ef527e1b",
      "backgroundColour": "#9f0500",
      "foregroundColour": "#FFFFFF",
      "comment": "Wayfarers sartorial authentic, small batch readymade disrupt coloring book.",
      "description": "Wayfarers sartorial authentic, small batch readymade disrupt coloring book.",
      "lastChanged": "2017-07-03T09:25:52.955293Z",
      "revision": 2
    }
  ]
}

• I can see that the serializer .is_valid() is True for the PolicySerializer
• When I look at validated_data those three fields are missing (the rest are there)
• I've tried commenting out the read_only_fields and that doesn't seem to make any difference
• I've been referencing the DRF documentation here
  

My question: How do I get the identifier field within the validated_data of the nested representation?